Back hoe construction



`lune 30, 1964 Filed May 28, 1962 D. l. BURKHART BACK HOE CONSTRUCTION 3 Sheets-Sheet 1 iwf/Zar N m June 30, 1954 D. l. BURKHART BACK HOE CONSTRUCTION 3 Sheets-Sheet 2 Filed May 28, 1962 zwi 7% ..5 .Qmf w@ INN June 30, 1964 D. l. BURKHART BACK HOE CONSTRUCTION 5 Sheets-Sheet 3 Filed May 28, 1962 United States Patent O 3,139,200 BACK HOE CONSTRUCTION Donald I. Burkhart, Milwauke, Oreg., assignor to Esco Corporation, a corporation of Oregon Filed May 28, 1962, Ser. No. 198,225 10 Claims. (Cl. 214-138) This invention relates to back hoe construction, and, more particularly, to a novel pitch brace therefor.

Heretofore, it has been the practice in some instances to interconnect the bucket and dipper stick of a back hoe with a bracing member generally known to the art as a pitch brace. This has provided some stabilization of the bucket during digging, the motion of the bucket being induced usually through cables and pulleys provided between the bucket and the main frame of the vehicle carrying the back hoe. However, the stabilization heretofore achieved through the use of a rigid pitch brace has been at the expense of an advantageous versatility of operation, necessitating considerable hand labor in the digging of trenches, ditches, etc. Through the novel pitch brace herein provided, I find that the effectiveness of a back hoe can be materially increased, not only in terms of the volume of material moved, but also in terms of the life of the equipment. Here, it will be appreciated that the shock forces imposed on the bucket may distort or even rupture certain of the other articulatable elements making up the back hoe so that extensive and expensive down-time is required.

It follows, therefore, that a principal object of this invention is to provide a novel pitch brace capable of improving the performance or" a back hoe along the lines indicated above.

Another object is to provide a novel back hoe which features an extendable pitch brace, i.e., an hydraulic cylinder and piston rod unit which provides for an operation heretofore not available to those in this art.

Still another object is to provide a hydraulic pitch brace making use of a cylinder and piston rod unit equipped with suitable exterior telescoping sleeves which provide an advantageous function in stabilizing the structure against side loads.

Yet another object is to provide a hydraulic pitch brace utilizing a unique fluid supply system wherein valving is employed to maintain the pitch brace in a given extension without the need of continually applying pressure iluid from a remote source.

Other objects and advantages of the invention may be seen in the details of construction and operation set down in this specication.

The invention will be described in conjunction with an illustrative embodiment in the accompanying drawing, in which- FIG. 1 is an elevational View of a crawler-equipped cab having `the inventive back hoe movably secured thereto, an alternative position of the bucket due to extension of the pitch brace being shown in dotted line;

FIG. 2 is a fragmentary elevational view of the back hoe of FIG. 1 showing the bucket in a condition of breaking olf humps in a rock bottom;

FIG. 3 is a view similar `to FIG. 2 but showing the back hoe in various operative positions as would be encountered when excavating around a submerged pipe;

FIG. 4 is an end elevational view of the working end of the back hoe seen in the preceding iigures;

FIG. 5 is a plan elevational view of the hydraulic pitch brace of the invention;

FIG. 6 is a side elevational view, partially broken away, of the structure seen in FIG. 5;

FIG. 7 is an end elevational view of the structure of FIG. 5 looking toward the butt end of the cylinder provided as part of the hydraulic pitch brace;

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FIG. 8 is an end elevational view of the FIG. 5 constrlction looking toward the free end of the piston rod; an

FIG. 9 is a longitudinal sectional View taken along the axis of the structure shown in FIG. 5.

In the illustration given, and with reference to FIG. l, the numeral 10 designates generally a vehicle for performing a back hoe operation, the vehicle 10 including a cab 11 supported on crawlers 12. The cab 11 carries a hydraulic liuid system generally designated 13, and, at the operator end, a boom 14. Aiiixed to the end of the boom 14 for pivotal movement is a dipper stick 15, and at the lower end of the dipper stick is provided a bucket 16 suitably equipped with a front end lip 17 on which are mounted digger teeth 18 (see FIG. 4). The dipper stick 15 is actuated through the usual pulley and cable system 19, while another conventional pulley and cable system 20 is provided to cooperate with system 19 to move the stick and bucket assembly relative to the boom 14. The foregoing description has been made brief, since the elements generally described are well known to those in the excavation art, as is the general operation of the back hoe wherein the bucket is moved in an angularly upward path toward the cab 11 in excavation.

The inventive pitch brace is designated generally by the numeral 21 and is seen to extend between lugs 22 on the dipper stick and a projection 23 on the upper open side of the bucket 16. In the illustration given, the dipper stick is pivotally connected to the bucket as at 24-the extreme rear end of the bucket-while the cable and pulley systern 2l) is connected to the bucket at 25, near the front lip 17. The pitch brace 21 is seen to be connected to the bucket between the points 25 and 24, the point of connection in FIG. 1 being designated by the numeral 26.

The pitch brace 21 is seen in enlarged forrn in FIG. 5, and is seen to include a cylinder and piston rod unit generally designated 27. The unit 27 includes a cylinder 28 suitably equipped at its butt end with an eye or lug 29 for pivotal interconnection with a supporting structure. The piston rod end of the cylinder 28 has the piston rod 30 projecting therefrom, Ithe piston rod 30 also being equipped with the usual pivot coupling as is designated by the numeral 31.

Connected to the lug 29 by means of a square-headed pin 32 is a lower 'end weldment generally designated by the numeral 33. The weldment 33, which can also be seen in FIG. 7, has a generally tubular body 34 defining a sleeve to which are secured wings or ins 35. The wings or iins 35 project outwardly beyond the lug 29 and dene spaced-apart mounting clevises 36. In the illustration given, the clevises 36 are the portions secured to the bucket 16 as at 26.

At its upper end, the weldment 33 is equipped with an interrupted flange 37, to which is bolted a guide weldment generally designated 38. The element 38 is seen to thus provide an extension of the weldment 33, projecting beyond the piston rod end of the cylinder 28. The guide weldment 38 is equipped with flanges 39 matable with the flanges 37 of the lower end weldment 33 and secured thereto by bolts 40.

The bore of the guide weldment 38 is equipped with two annular bushings as at 41, through which an inner sleeve 42 slides, the sleeve 42 being provided as part of the upper end weldment generally designated 43. A seal 41a is provided at the upper end to exclude dirt and moisture from the sliding surface of sleeve 42. The upper end weldment is secured by means of a square-headed pin 44 to the lug or eye 31 of the piston rod 30. The generally tubular body 45 (see FIG. 8) of the upper end weldment 43 carries spaced-apart clevises 46 which are secured to the dipper stick as at 22 in FIG. 1.

Still referring to FIG. l, the hydraulic system 13 includes a high pressure hydraulic pump 47 and a low pressure hydraulic pump 48 connected by a conduit 49 to an oil tank 50. The pumps 47 and 48 are connected by means of a conduit 51 to Va control valve 52, while the tank 50 is connected to the control valve 52 by means of a conduit 53. The control valve 52 is connected by means of two conduits 54 running along the boom 14 to a holding valve 55, and the holding valve 55 is connected by means of flexible connectors 56' to the hydraulic pitch brace 21, i.e., the cylinder 28, the connectors 56 also being seen in FIG. 5.

In an actual embodiment of the invention, the holding valve 55 was a Sarasota 25720-6, set for 3,000 p.s.i., while the control valve was a Dukes L-1700. The high pressure pump 47 was a Webster JDS, rated at 8 g.p.m. at 2,000 p.s.i., while the low pressure pump 48 was a Webster 3-HCS, rated at 16 g.p.rn. at 1,000 p.s.i. The pitch brace 2l had a length 651/2 between clevises in the piston rod retracted condition, and S8 in the piston rod extended condition.

The operation and performance characteristics as set forth below were determined through the use of a pitch brace and hydraulic system of the character just described when installed on a Link-Belt LS 98 Back Hoe, with an Esco l yard hoe dipper. The adjustable pitch brace 21 had a 221/2 stroke, which yielded 43 of tooth movement through 32 of angle. All side loads applied to the buckets were taken through the sliding tubular sleeve elements made up kof the weldments 33, 38 and 43. The 2,000 p.s.i. high pressure pump gave l tons of prying force at the teeth under any digging condition, and the 1,000 p.s.i. high volume pump gave full adjustment in less than 10 seconds. The inventive installation was found to save 35% in digging time on a four-day sewer job in dirt. This ditch ranged from 22 to l0 deep, with many obstructions, both above and below ground. Hand digging was virtually eliminated, and the machine dug almost continuously. In tough lava rock, where two weeks of chopping had previously netted only a few feet of ditch and much damage to the machine, the same machine, with the hydraulic pitch brace operating, dug the whole ditch in eight days, with no damage to the equipment and 50% less chopping. Y

The versatility of the bucket movement through the inventive construction can be appreciated from FIG. 1, where the alternative position 16a of the bucket 16 is spaced about an angular distance of 32-this representing 4'3" at the teeth, which could be changed in l0 seconds. Thekapplication of 44,000 lbs. of hydraulic force in the pitch brace 21 resulted in 20,000 lbs. of force atV the teeth. The further versatility of the inventive construction can be appreciated in that merely by removing the machine bolts 32 and 44, the entire cylinder and piston rod can be removed from the lower end of the hydraulic pitch brace 21, i.e., through the open end of the lower end weldment 33.

The use ofthe hydraulic pitchbrace and its large dea can be performed even under an obstruction. In FIG. 3,

the bucket is again designated by the numeral 16 and is seen to be positioned below the surface of the ground 57, as in a trench 58. Located above the lower floor of the trench 58 is a pipe 59.' The mound area designated by the numeral `60 is the area that cannot be reached with the conventional clipper angle, but it can be seen that merely by relocating the vehicle and changing the length designatedY b in FIG. 3 Vshows that the bucket extends to dig further under the obstruction than with previous arrangements. The upper dotted line configuration designated 16C demonstrates that the hydraulic pitch brace 2l can be retracted to clear the obstruction without spilling the load.

It has also been found that the bucket i6 can pick up boulders twice as big, or larger heap loads of wet material, between the sheave housing as at 20a in FIG. l and the teeth 18, than prior constructions. Further, the inventive construction makes possible improved dumping and a shorter cycle for it, even in close quarters.

The illustration in FIG. 2 demonstrates that the bucket teeth can exert 20,500 lbs. of constant force at the extreme reach, where the pull in a normal construction is only 7,000 lbs. at the teeth.

Along with the substantially enhanced versatility of the back hoe, Ythere are provided safeguards against damage.V The pressure-limiting valve 55 relieves high shock pressure at the cylinder, eliminating danger of breaking hoses and fittings in the hydraulic system.

The pitch brace itself, with the coaxially disposed telescoping sleeve, takes up the large side moments resulting from a chopping shock on one tooth, so that the cylinder is protected from all but straight push-pull loads. Further, there is present in the inventive construction a cushioning effect through the use of the limiting valve 55 and the hydraulic fluid to reduce shock wear on the connecting pins and teeth.

While, in the foregoing specification, I have set down a detailed description of an embodiment of the invention for the purpose of illustration thereof, many variations in the details herein given may be made by those skilled in the art without departing from the spirit and scope of the invention.

I claim:

l. In a back hoe,

(A.) a frame providing a movable mounting for a boom,

(B) a boom pivotally connected adjacent one end thereof to said frame, means for pivoting said boom relative to said frame,

(C) a Clipper stick pivotally connected adjacent one end e thereof to said boom adjacent the other end of saidv boom, means for pivoting said clipper stick relative to said boom,

(D) a bucket pivotally connected to said flipper stick adjacent the other end of said clipper stick, said bucket having a front lip facing said frame during an angularly upward digging operation, said dipper stick being connected to a rear portion of said bucket,

(E). means interconnecting said bucket and frame for pivoting said bucket relative to said dipper stick, and

(F) cylinder and piston rod unit means interconnecting said bucket and dipper stick, the connection of said unit means with said bucket being between said lip and said rear portion, said unit means including an externally telescoping sleeve coaxially reiated to the piston rod of said unit means.

2. The structure of claim l in which said frame is equipped with a hydraulicsystem for powering said unit means, -and a valve interposed in said system for maintaining a chosen position of said unitrneans while permitting. circulation of hydraulic iiuid in said system at lower pressure than that required to maintain said unit means in said chosen position.

' 3. For a back hoe having a movable frame equipped with articulatable boom, clipper stick and bucket elements for relative intermovement and wherein the bucket is equipped with a lip confronting the frame during an angularly upward digging operation, an improved pitch brace comprising a cylinder and piston rod unit pivotally interconnected between said bucket element and the portion of said dipper stick element confronting said frame during said operation, and an extensible casing about said unit, said casing including a first sleeve member mounted on the piston rod of said unit in coaxial relation therewith, and a second sleeve member mounted on the cylinder of said unit in coaxial relation therewith, said members being arranged in telescoping relation.

4. The structure of claim 3 in which said lirst member is received Within said second member.

5. The structure of claim 4 in which said second sleeve member includes two portions arranged in end-to-end relation, one of said portions extending beyond the piston rod end of said cylinder and providing a seal for said first sleeve member.

6. A pitch brace for a back hoe, comprising (A) a cylinder and piston rod unit,

(B) means for supplying pressurized fluid to the cylinder of said unit for extending and retracting the piston rod thereof,

(C) pivot connection means on the butt end of said cylinder and on the free end of said piston rod,

(D) a rst sleeve element coaxially related to said cylinder and coupled to said cylinder connection means, said irst sleeve element being equipped with pivot connection means spaced axially of said cylinder connection means, and

(E) a second sleeve element coaxially related to said piston rod and coupled to said piston rod connection means, lSaid second sleeve element being equipped with pivot connection means `spaced axially of said piston rod connection means, said rst and second sleeve elements being telescopically related.

7. The structure of claim 6 in which said fluid-supplying means includes conduit means communicating with said cylinder and valve means in lsaid conduit means for maintaining said piston rod in a given position independently of the pressure of uid supplied to said valve means.

8. The structure of claim 6 in which said rst sleeve element is equipped with a portion extending axially beyond the piston rod end of said cylinder, said portion being equipped with an annular seal for said second sleeve element.

9. In a back hoe, a frame providing a movable mounting for a boom, a boom pivotally connected adjacent one end thereof to Said frame, means for pivoting said boom relative to said frame, a dipper stick pivotally connected adjacent one end thereof to said boom adjacent the other end of said boom, means for pivoting said dipper stick relative to said boom, a bucket pivotally connected to said dipper stick adjacent the other end o-f said dipper stick, said bucket having a front lip facing said frame during an angularly upward digging operation, said dipper ystick being connected to a rear portion of said bucket, means interconnecting said bucket and frame for pivoting Said bucket relative to said dipper stick, and a hydraulic cylinder interconnecting said bucket and dipper stick, said cylinder having a piston rod projecting from one end thereof coupled to said dipper stick and clevis means at the other end coupled'to said bucket between said lip and rear portion, means operatively associated with said piston rod for stabilizing the same against radial stresses, and valve-equipped conduit means for supplying hydraulic luid to said cylinder one end.

10. The structure of claim 9 in which said conduit means includes a pair of pumps operating at different pressures, the pump with the higher operating pressure being adapted to increase the digging force at the bucket front lip, while the pump with the lower operating pressure is adapted to rapidly change the position of said piston rod.

References Cited in the le of this patent UNITED STATES PATENTS 1,385,322 Hoffmeyer July 19, 1921 2,303,852 Linn Dec. 1, 1942 2,305,566 Weston et al Dec. 15, 1942 

1. IN A BACK HOE, (A) A FRAME PROVIDING A MOVABLE MOUNTING FOR A BOOM, (B) A BOOM PIVOTALLY CONNECTED ADJACENT ONE END THEREOF TO SAID FRAME, MEANS FOR PIVOTING SAID BOOM RELATIVE TO SAID FRAME, (C) A DIPPER STICK PIVOTALLY CONNECTED ADJACENT ONE END THEREOF TO SAID BOOM ADJACENT THE OTHER END OF SAID BOOM, MEANS FOR PIVOTING SAID DIPPER STICK RELATIVE TO SAID BOOM, (D) A BUCKET PIVOTALLY CONNECTED TO SAID DIPPER STICK ADJACENT THE OTHER END OF SAID DIPPER STICK, SAID BUCKET HAVING A FRONT LIP FACING SAID FRAME DURING AN ANGULARLY UPWARD DIGGING OPERATION, SAID DIPPER STICK BEING CONNECTED TO A REAR PORTION OF SAID BUCKET, 